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Coupled functional physiological phenotyping and simulation model to infer the transpiration sensitivity traits and its implications for transpiration ideotype design

As agricultural drought becomes more frequent worldwide, it is essential to improve crop productivity whilst reducing the water consumption to achieve a sustainable production. Plant transpiration rate and water use efficiency (WUE) collectively determine the yield performance, yet it is challenging to balance the two in breeding programs due to still insufficient mechanistic understanding of the traits. Here we demonstrate the feasibility and effectiveness of calculating dynamic and momentary WUE by coupling WUE model and the state-of-the-art functional physiological phenotyping (FPP). We also present the method of quantifying genotype-specific traits reflecting sensitivity of transpiration to radiation (STr-Rad) and vapor pressure deficit (STr-VPD), under evolving developmental stage and water availability. Using these methods, we revealed the genotypic difference of STr-Rad and STr-VPD in three watermelon accessions, the dramatic change in each of them across the drought treatment phases, and the quantitative impacts of them on dynamic WUE patterns. Based on our results and computational simulations, a general principle for transpiration ideotype design is proposed, which highlights the benefits of lowering STr-VPD to increase WUE and increasing STr-Rad to offset the decline of Tr. FPP-enabled phenomic selection will help screen for elite crops lines with desired transpiration sensitivities.

physiology↗

Can increased prenatal exposure to thyroid hormones alter physiology and behaviour in the long-term? Insights from an experimental study in Japanese quails.

Maternal thyroid hormones (triiodothyronine T3 and thyroxine T4) are important regulators of embryonic development and gene expression. While maternal thyroid disorders are known to cause developmental issues in humans, variation in maternal thyroid hormones in healthy mothers have also been found to correlate with infant and child phenotypes. This suggests a potential impact of maternal thyroid hormones on offspring phenotype in an eco-evolutionary context. In chickens, prenatal thyroid hormone treatment has been shown to influence embryonic gene expression and postnatal treatment to influence imprinting and learning. However, the potential long-term effects of maternal thyroid hormones on physiology and behaviour are unclear. This study aims to investigate the long-term effects of maternal thyroid hormones on behaviour, plasma thyroid hormone levels and brain gene expression using the Japanese quail (Coturnix japonica) as a model. Egg hormone levels were elevated by injecting unincubated eggs with either saline (control), T3, T4 or a mixture of T3 and T4. Social motivation, boldness and fearfulness to predators were tested shortly after hatching and as adults. Plasma thyroid hormone levels and pallial expression of thyroid hormone receptor A, type 2 deiodinase, and nuclear receptor coactivator 1 were measured in adulthood. We found no evidence that elevated thyroid hormone levels in eggs affected behaviour, plasma hormone levels, or gene expression. This is the first study examining the potential long-term effects of elevated maternal thyroid hormones within the natural range. Although we found no evidence of long-term effects, other traits may still be affected and remain to be studied.

physiology↗

Physiological accuracy in simulating refractory cardiac tissue: the volume-averaged bidomain model vs. the cell-based EMI model

The refractory period of cardiac tissue can be quantitatively described using strength-interval (SI) curves. The information captured in SI curves is pertinent to the design of anti-arrhythmic devices including pacemakers and implantable cardioverter defibrillators. As computational cardiac modelling becomes more prevalent, it is feasible to consider the generation of computationally derived SI curves as a supplement or precursor to curves that are experimentally derived. It is beneficial, therefore, to examine the profiles of the SI curves produced by different cardiac tissue models to determine whether some models capture the refractory period more accurately than others. In this study, we compare the unipolar SI curves of two tissue models: the current state-of-the-art bidomain model and the recently developed extracellular-membrane-intracellular (EMI) model. The EMI models resolution of individual cell structure makes it a more detailed model than the bidomain model, which forgoes the structure of individual cardiac cells in favour of treating them homogeneously as a continuum. We find that the resulting SI curves elucidate differences between the models, including that the behaviour of the EMI model is noticeably closer to the refractory behaviour of experimental data compared to that of the bidomain model. These results hold implications for future computational pacemaker simulations and shed light on the predicted refractory properties of cardiac tissue from each model. Author summaryMathematical modelling and computational simulation of cardiac activity have the potential to greatly enhance our understanding of heart function and improve the precision of cardiac medicine. The current state-of-the-art model is the bidomain model, which considers a volume average of cardiac activity. Although the bidomain model has had success in several applications, in other situations, its approach may obscure critical details of heart function. The extracellular-membrane-intracellular (EMI) model is a recently developed model of cardiac tissue that addresses this limitation. It models cardiac cells individually; therefore, it offers significantly greater physiological accuracy than bidomain simulations. This increase in accuracy comes at a higher computational cost, however. To explore the benefits of one model over the other, here we compare the performance of the bidomain and EMI models in a pacing study of cardiac tissue often employed in pacemaker design. We find that the behaviour of the EMI model is noticeably closer to experimental data than the behaviour of the bidomain model. These results hold implications for future pacemaker design and improve our understanding of the two models in relation to one another.

physiology↗

Kir7.1 is the physiological target for hormones and steroids that regulate uteroplacental function

Preterm birth is a multifactorial syndrome that is detrimental to the well-being of both the mother and the newborn. During normal gestation, the myometrium is maintained in a quiescent state by the action of progesterone. As a steroid hormone, progesterone is thought to modify uterine and placental morphology by altering gene expression, but a nongenomic mode of action has long been suspected. Here we reveal that progesterone activates both human and murine inwardly rectifying potassium channel Kir7.1, which is expressed in mammalian myometrial smooth muscle and placental pericytes during late gestation. Kir7.1 is also activated by compounds used to prevent premature labor, including the progestogens 17-alpha-hydroxyprogesterone caproate and dydrogesterone, revealing an unexpected mode of action for these drugs. Our results reveal that Kir7.1 is the molecular target of a number of endogenous and synthetic steroids that control uterine excitability and placental function, and is therefore a promising therapeutic target to control utero-placental physiology and support healthy pregnancy.

physiology↗

Gut physiology of rainbow trout (Oncorhynchus mykiss) is influenced more by 1 short-term fasting followed by refeeding than by feeding fishmeal-free diets

Supplementing a fishmeal-free diet with yeast extract improves rainbow trout (Oncorhynchus mykiss) growth performance and modulates the hepatic and intestinal transcriptomic response. These effects are often observed in the long term, but are not well documented after short periods of fasting. Fasting for a few days is a common practice in fish farming, especially before handling the fish, such as for short sorting, tank transfers and vaccinations. In the present study, rainbow trout were subjected to a four-day fast and then refed, for eight days, a conventional diet containing fishmeal (control diet) or alternative diets composed of terrestrial animal by-products supplemented or not with a yeast extract. During the refeeding period alone, most of the parameters considered did not differ significantly in response to the different feeds. Only the expression of claudin-15 was upregulated in fish fed the yeast-supplemented diet compared to the control diet. Conversely, fasting followed by refeeding significantly influenced most of the parameters analyzed. In the proximal intestine, the surface area of villi significantly increased and the density of goblet cell tended to decrease during refeeding. Although no distinct plasma immune response or major signs of gut inflammation were observed, some genes involved in the structure, complement pathway, antiviral functions, coagulation and endoplasmic reticulum stress response of the liver and intestine were significantly regulated by refeeding after fasting. These results indicate that short-term fasting, as commonly practiced in fish farming, significantly alters the physiology of the liver and intestine regardless of the composition of the diet.

physiology↗

Physiological adaptation to high irradiance in duckweeds depends on light habitat niche and is ecotype and species-specific.

Duckweeds are free-floating aquatic organisms with species ranging from 2 mm-10 mm, where each plant is a single leaflike structure. Recognized as an emerging food crop, their fast growth rates offer potential for cultivation in closed systemsHowever the majority of available duckweed clones lack information regarding habitat origin and physiology. We describe a novel UK collection derived from low light (dLL) or high light (dHL) habitats and profiled for growth, photosynthesis and photoprotection (Non Photochemical Quenching, NPQ) responses. Multiple ecotypes of three Lemna species and one ecotype of Spirodela polyrhiza, were grown under low light (LL:100 mol m-2 s-1) and high light (HL:350 mol m-2 s-1). We found species and ecotypic variation in photosynthesis acclimation. Duckweeds grown under HL exhibited lower growth rate, biomass, chlorophyll and quantum yield of photosynthesis. In HL-compared to LL, carotenoid de-epoxidation state and NPQ were higher whilst photosystem II efficiency ({phi}PSII) and chla:b ratios were unchanged. Interestingly dLL plants showed relatively stronger acclimation to HL compared to dHL plants: These ecotypes achieved faster growth in HL: by area and colony gain, higher carotenoid levels and less degradation of chlorophyll. We conclude that adaptation to local habitat among ecotypes strongly affects performance under controlled conditions.

physiology↗

Physiological variability in mitochondrial rRNA predisposes to metabolic syndrome

Metabolic syndrome is a growing concern in developed societies, and due to its polygenic nature, the genetic component is only slowly being elucidated. Common mitochondrial DNA sequence variants have been associated with symptoms of metabolic syndrome and may be relevant players in the genetics of metabolic syndrome. We investigate the effect of mitochondrial sequence variation on the metabolic phenotype in conplastic rat strains with identical nuclear but unique mitochondrial genomes, challenged by high-fat diet. We find that the variation in mitochondrial rRNA sequence represents a risk factor in insulin resistance development, which is caused by diacylglycerols accumulation induced by tissue-specific reduction of the oxidative capacity. These metabolic perturbations stem from the 12S rRNA sequence variation affecting mitochondrial ribosome assembly and translation. Our work demonstrates that physiological variation in mitochondrial rRNA might represent a relevant underlying factor in the progression of metabolic syndrome. Competing interestsThe authors declare that no competing interests exist.

physiology↗

Behavioural responses to acute warming precede critical shifts in the cellular and physiological thermal stress responses in fish

From a conservation perspective, it is important to identify when sub-lethal temperatures begin to adversely impact an organism. However, it is unclear whether, during acute exposures, these cellular thresholds occur at similar temperatures to other physiological or behavioural changes. To test this, we estimated temperature preference (15.1 {+/-} 1.1 {degrees}C) using a shuttle box, thermal optima for aerobic scope (10-15 {degrees}C) using respirometry, agitation temperature (22.0 {+/-} 1.4 {degrees}C) as the point where a fish exhibits a behavioural avoidance response and the CTmax (28.2 {+/-} 0.4 {degrees}C) as the upper thermal limit for 1 yr old Brook Trout (Salvelinus fontinalis) acclimated to 10 {degrees}C. We then acutely exposed a different subset of fish to these temperatures and sampled tissues when they reached the target temperature or after 60 min of recovery at 10 {degrees}C. We used qPCR to estimate mRNA transcript levels of genes associated with heat shock proteins, oxidative stress, apoptosis, and inducible transcription factors. A major shift in the transcriptome response occurred near the agitation temperature, which may identify a link between the cellular stress response and the behavioural avoidance response.

physiology↗

Pulmonary Fibrosis Ferret Model Demonstrates Sustained Fibrosis, Restrictive Physiology, and Aberrant Repair

RationaleThe role of MUC5B mucin expression in IPF pathogenesis is unknown. Bleomycin-exposed rodent models do not exhibit sustained fibrosis or airway remodeling. Unlike mice, ferrets have human-like distribution of MUC5B expressing cell types and natively express the risk-conferring variant that induces high MUC5B expression in humans. We hypothesized that ferrets would consequently exhibit aberrant repair to propagate fibrosis similar to human IPF. MethodsBleomycin (5U/kg) or saline-control was micro-sprayed intratracheally then wild-type ferrets were evaluated through 22 wks. Clinical phenotype was assessed with lung function. Fibrosis was assessed with {micro}CT imaging and comparative histology with Ashcroft scoring. Airway remodeling was assessed with histology and quantitative immunofluorescence. ResultsBleomycin ferrets exhibited sustained restrictive physiology including decreased inspiratory capacity, decreased compliance, and shifted Pressure-Volume loops through 22 wks. Volumetric {micro}CT analysis revealed increased opacification of the lung bleomycin-ferrets. Histology showed extensive fibrotic injury that matured over time and MUC5B-positive cystic structures in the distal lung suggestive of honeycombing. Bleomycin ferrets had increased proportion of small airways that were double-positive for CCSP and alpha-tubulin compared to controls, indicating an aberrant proximalization repair phenotype. Notably, this aberrant repair was associated with extent of fibrotic injury at the airway level. ConclusionsBleomycin-exposed ferrets exhibit sustained fibrosis through 22 wks and have pathologic features of IPF not found in rodents. Ferrets exhibited proximalization of the distal airways and other pathologic features characteristic of human IPF. MUC5B expression through native cell types may play a key role in promoting airway remodeling and lung injury in IPF.

physiology↗

NRBP1 and TSC22D proteins impact distal convoluted tubule physiology through modulation of the WNK pathway

The With No lysine (WNK) kinases regulate processes such as cell volume and epithelial ion transport through the modulation of Cation Chloride Cotransporters such as the NaCl cotransporter, NCC, present in the distal convoluted tubule (DCT) of the kidney. Recently, the interaction of WNKs with Nuclear Receptor Binding Protein 1 (NRBP1) and Transforming Growth Factor {beta}-Stimulated Clone 22 Domain (TSC22D) proteins was reported. Here we explored the effect of NRBP1 and TSC22Ds on WNK signaling in vitro and in the DCT. TSC22D1.1, TSC22D2, and NRBP1 are localized in DCT WNK bodies, which are cytoplasmic biomolecular condensates associated with WNK activation. In HEK293 cells, long TSC22D isoforms and NRBP1 increase WNK4 activity. DCT-specific NRBP1 knockout mice have reduced NCC phosphorylation and activate a compensatory response. Thus, NRBP1 and long TSC22D proteins are positive modulators of WNK signaling and modulate Na+ reabsorption in the kidney. NRBP1 and TSC22Ds likely influence WNK signaling in other tissues, impacting various physiological processes. TeaserThe pseudokinase NRBP1 and its associated TSC22D proteins modulate WNK kinases to regulate sodium reabsorption in the kidney.

physiology↗

Relaxin signaling is critical for virgin female reproductive physiology in Drosophila

Ovulation enables mature oocytes to exit the ovary for potential fertilization. In Drosophila, ovulation is induced by mating but also occurs spontaneously in virgins, with rates varying widely in natural populations: short oocyte retention is ancestral, while longer retention is favored in colder climates. The molecular regulation of spontaneous ovulation remains unclear. Here, we show that disrupting the relaxin/insulin-like peptide Dilp8 or its receptor Lgr3--an orthologue of vertebrate RXFP1/2--in follicle cells or specific neurons, respectively, delays ovulation, slows average egg transit time in the reproductive tract, and facilitates oogenesis progression beyond [~]2 mature oocytes per ovariole, leading to mature follicle accumulation in the ovary. Mating largely rescues these defects, suggesting the pathway is dispensable post-mating. Dilp8-Lgr3 signaling ensures high oocyte quality by promoting elimination of lower-quality aging oocytes and by antagonizing oogenesis progression via an undefined mechanism downstream of Lgr3+ neurons. Our findings provide a molecular basis for oocyte retention time regulation in Drosophila involving ovarian-nervous system cross-talk, and bring further support for an ancient, conserved role for relaxin-like signaling in regulating ovulation and overall female reproductive physiology. Summary statementThis study uncovers how ovary-neuron communication promotes spontaneous ovulation and prevents buildup of aging eggs, ensuring optimal egg quality in fruit flies.

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Perinatal Asphyxia Alters Physiological Responses and Ex Vivo Cardiovascular Function of Preterm Growth-Restricted Lambs

IntroductionFetal growth restriction (FGR) arises from chronic hypoxia and increases the risk of cardiovascular dysfunction following perinatal asphyxia, although the underlying mechanisms are unknown. We investigated whether FGR lambs have altered cardiovascular responses to perinatal asphyxia compared to control lambs, and whether impairments in 1 and {beta}1 adrenergic receptor function underlie these responses. MethodsSingle or twin-bearing ewes underwent sterile fetal surgery at 89 days gestation (dGA; term=148d) to induce FGR (single umbilical artery ligation) or sham surgery (Control). At 126dGA, lambs were delivered via caesarean section, instrumented and randomised to immediate ventilation (ControlVENT n=6; FGRVENT n=6), or asphyxia (ControlASPHYXIA n=12; FGRASPHYXIA n=11) induced by umbilical cord occlusion while withholding resuscitation until diastolic blood pressure (BP) decreased to 10mmHg. Lambs were ventilated for 8 hours before baseline ex vivo cardiac function was assessed via Langendorff perfusion to measure left ventricular developed pressure (LVDP), heart rate (HR) and coronary perfusion pressure (CPP). Ex vivo 1 and {beta}1 adrenergic responses were assessed via phenylephrine (10-5 to 10-2 mmol/L) and dobutamine (10-7 to 10-4) administration, respectively. ResultsFGRASPHYXIA lambs had lower BP during asphyxia (p<0.05 vs ControlASPHYXIA) and took longer to reach a diastolic BP of 10mmHg (14.5 {+/-} 0.8 min vs. 19.2 {+/-} 1.3 min; p=0.005). FGRASPHYXIA lambs had lower BP in the first 5 minutes after return of spontaneous circulation (p<0.05) due to impaired vascular contractility, with reduced Tau, dP/dtmax and dP/dtmin (p<0.03 vs ControlASPHYXIA). Baseline LVDP, HR and CPP were similar between groups, however FGRASPHYXIA lambs had increased LVDP responses to phenylephrine and dobutamine (p<0.05 vs ControlASPHYXIA), without significant changes to HR or CPP. ConclusionFGR lambs have altered physiological responses to perinatal asphyxia due to impaired vascular contractility and dysregulated cardiac 1 and {beta}1 adrenergic receptor function, which may increase susceptibility to cardiovascular dysfunction in the neonatal period.

physiology↗

"Smurf Mice": revolutionising our understanding of age-related and end-of-life animal physiology

Living animals reach their end-of-life through a stereotypic set of fascinating but poorly understood processes. The discovery, first in flies and later in nematodes and zebrafish, of the "Smurf phenotype" is a central tool for picking this complex "lock of biology", that one of ageing. Using the Smurfs, we have shown an evolutionarily conserved end-of-life transition across Drosophilids, nematodes and zebrafish. This tool has been key to identify the discontinuous nature of ageing and predict impending death from natural causes as well as from environmental stresses. This phenotype allowed us to discover that ageing is made up of two successive phases : a first phase where individuals are healthy and have no risk of mortality, but show an age-dependent and increasing risk of entering a second phase, characterized by the so-called hallmarks of ageing and a high risk of death. Here, we test whether these two consecutive phases of ageing separated by the Smurf transition are a conserved feature of ageing in the mammals using Mus musculus as a model. We performed a longitudinal longevity study using both males and females from two different mouse genetic backgrounds and by integrating physiological, metabolic and molecular measurements with the life history of approximately 150 mice. We show the existence of a phenotypic signature typical of the last phase of life, observable at any chronological age. Validating the two-phase ageing model in a mammalian organism allows better characterized the high risk of imminent death and would extend its implications to a broader range of species for ageing research.

physiology↗

The menstrual cycle through the lens of a wearable device: insights into physiology, sleep, and cycle variability

Women on average have 450 menstrual cycles in a lifetime, but we lack a characterization of physiological biometrics across the cycle and lifespan. We analyzed 1.2 million days of data from 2,596 women who logged 42,759 menstrual cycles and wore a device that collected sleep and biometric data including resting heart rate (RHR), heart rate variability, respiratory rate, skin temperature, and blood oxygen saturation level. We generated novel quantifications of daily biometrics across ages and cycle lengths, finding that cycle length is strongly associated with how much cardiorespiratory metrics vary across the cycle. We observed greater cycle variability for participants who slept 6 versus 8 hours. A within-participant natural experiment showed that decreased sleep resulted in biometric changes regardless of cycle phase (e.g., RHR increased 1.2% with a 10% decrease in weekly sleep duration). These results lay a foundation to better understand and optimize female health and performance.

physiology↗

Within-subject rhythmicity and stability of hunger, satiety, and physiological markers: insights from a five-day laboratory study in time-isolation conditions

Hunger and satiety are interoceptions involved in the control of food intake. How they change across the day and from one day to the next, as well as their relationships with physiological parameters, remain poorly understood. In a five-day laboratory study, twenty healthy male participants (24.2 {+/-} 3.3 years) were given three meals per day (breakfast, lunch, dinner), at times based on each individuals internal time. Subjects had an 8-h sleep opportunity at night recorded by polysomnography, during which time they were exposed to 4 different light intensities (0, 3, 8, or 20 lux). Hunger and satiety were assessed before and after each meal. Heart rate was measured continuously and glucose levels were sampled every 15 minutes. We found that: 1) Hunger and satiety varied dynamically with the lowest levels at breakfast and the highest at lunch and dinner (p < 0.01); 2) the intensity of hunger and satiety remained stable across the five experimental days, and were subject-dependent; 3) Heart rate was higher after than before meals (p < 0.0001), and higher around breakfast than dinner; 4) Glycemia before and after meals was respectively stable throughout the day and over the study period; 5) Interoception was correlated with fluctuations in heart rate, glucose levels and sleep duration. Overall, our results reveal that hunger and satiety perception are individual characteristics. To better understand the role of interoception in food intake control, both hunger and satiety should be measured, but separately in their respective states.

physiology↗

Lrrc55 modulates beta-cell resilience and calcium transporter expression under metabolic and physiologic stress

During pregnancy, pancreatic {beta}-cell mass and function are increased in adaptation to insulin resistance; this requires the action of prolactin receptor signaling. Recently, we discovered the Lrrc55, an auxiliary subunit of the voltage- and calcium-activated potassium channel (BK channel), is a prosurvival factor in {beta}-cell, and its expression and highly and specifically up regulated in the pancreatic islets during pregnancy. We found that overexpression of Lrrc55 protects {beta}-cells from glucolipotoxicity (GLT)-induced apoptosis. The protective effect of Lrrc55 is associated with dampening of the ER stress response and preservation of the releasable pool of calcium in the ER. Thus, we hypothesized that Lrrc55 protects {beta}-cells from GLT-induced ER stress and apoptosis by regulating ER calcium handling. Here, we report that Lrrc55 restored the GLT-mediated decrease in expression levels the insulin regulators, Pdx-1 and MafA, as well as the ER calcium regulator SERCA. Lrrc55 also attenuated the GLT-induced increase in expression of the ER calcium channel RyR2. Lrrc55 also attenuated GLT-mediated increase in protein expression of pro-apoptotic molecules CHOP and IRE1, and increased activation of the anti-apoptotic molecule Akt. However, Lrrc55 does not alter the activity levels of SERCA or IP3R under physiologic conditions. Transgenic mice with global deletion of Lrrc55 (Lrrc55-/-) are more susceptible to streptozotocin-induced diabetes. Surprisingly, Lrrc55-/- mice are more glucose tolerant and secreted more insulin during pregnancy. Together, these results suggest a role for Lrrc55 in maintaining expression of the ER calcium regulators in the presence of GLT but it may negatively regulate insulin secretion.

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High-salt diet disturbs the physiological uterine endothelial junction remodeling during pregnancy

A high-salt diet (HSD) induced excessive sodium intake is a major risk factor for various diseases. However, its specific effects on uterine endothelial cell and pregnancy outcomes remain poorly understood. In this study, we demonstrated that HSD induces gestation specific hypertension and adverse pregnancy outcomes in murine models. The proper spiral artery remodeling, which involved the decidual vascular endothelia, is thought to be essential for normal regulation of gestational blood pressure. We explored the molecular basis for the adaptation of vascular endothelial cell based on the transcriptome data, and uncovered the significant changes for the cell junction in the endothelia during this process. Furthermore, it was revealed that HSD induced more salt accumulation in the uteri and triggered the disturbed vascular endothelium cytoskeletal remodeling, which was associated impaired trophoblast cell invasion and incorporation into the vascular wall. Overall, our study identifies unique roles of decidual endothelium for pregnancy vascular remodeling, and demonstrates that HSD disrupts physiological spiral artery remodeling through endothelial maladaptation, which may concurrently induce systemic endothelial damage in maternal systemic vascular.

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Integrating physiology and transcriptomics reveals the mechanisms underlying the differences in cotton (Gossypium hirsutum L.) growth and development under different photoperiods

Photoperiod is a crucial environmental factor that regulates plant growth and flowering. While the photoperiodic flowering pathway has been extensively studied, the mechanisms underlying photoperiodic regulation of cotton (Gossypium hirsutum L.) growth and development remain unclear. In this study, we selected different genotypes of cotton varieties, XJ12 and XJ21-11, to investigate the effects of long-day (LD) and short-day (SD) conditions on cotton photosynthesis, dry matter accumulation, flowering time, and related gene expression, utilizing physiological index measurements, transcriptomics, and WGCNA analysis. The results indicated that LD treatment significantly enhanced photosynthetic parameters and dry matter weight in both cotton varieties, with the net photosynthetic rate (Pn) being 154.79% and 111.86% higher under LD compared to SD treatment. Additionally, the flowering time of the two varieties was advanced by 12 and 13 days, respectively, under LD treatment relative to SD treatment. LD conditions promoted gene expression in sucrose and starch metabolism, facilitating cotton growth. Furthermore, LD inhibited the expression of genes associated with flavonoid biosynthesis, thereby altering the secondary metabolism of cotton, and activated transcription factors through signaling pathways (including phytohormone signaling and MAPK signaling pathways) and biological clock rhythms, which induced earlier flowering in cotton. This study provides new insights into the molecular mechanism of the effect of photoperiod on cotton growth and development.

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